The present invention relates to a method and machine or apparatus for making cigarettes or the like. More particularly, the invention relates to improvements in a method and machine for making a continuous tobacco filler stream which can be converted into or constitutes a rod-like filler ready to be draped into a web of cigarette paper or other wrapping material to form therewith a rod adapted to be subdivided into plain cigarettes, cigars or cigarillos of unit length or multiple unit length. Still more particularly, the invention relates to a method and machine for making a continuous tobacco filler stream by resorting to one or more streams of suction air.
A cigarette making machine comprises a distributor wherein a magazine accumulates and maintains a supply of tobacco which contains relatively large particles (primarily shredded tobacco leaf laminae but normally also some comminuted ribs, stem and/or birds' eyes) as well as relatively small particles including so-called short tobacco or tobacco shorts and larger and smaller particles of tobacco dust. The distributor comprises means for withdrawing from the supply a continuous layer of tobacco whose contents are thereupon classified according to size and/or weight (e.g., by a winnower) so as to segregate particles of rock, metal or other foreign matter as well as ribs, stem and birds' eyes. The remaining material of the layer is converted into a relatively wide layer or carpet whose leading edge is showered into a stream building or growing zone in which the particles of the layer are converted into the filler stream. Such stream is usually trimmed, once or repeatedly, to form a rod-like filler which is ready for wrapping into cigarette paper. As a rule, the making of a filler stream and filler involves the use of large quantities of suction air (i.e., air which is maintained at less than atmospheric pressure), for example, to attract the material of the filler stream and/or filler to conveyors which advance the stream and/or filler toward the wrapping station. The utilization of large quantities of suction air invariably entails segregation of short tobacco and/or tobacco dust which must be separated from the gaseous carrier medium for a number of reasons, i.e., in order to avoid contamination of the plant as well as to recover the segregated material, especially short tobacco and larger particles of tobacco dust because the presence of such material in the filler is not objectionable; on the contrary, such material is often desirable because it enhances the uniformity of weight and/or the filling power of the rod-like filler in a cigarette or the like.
In accordance with presently prevailing practice, the suction air stream or streams which are used in cigarette making machines are caused to pass through a relatively large, complex and expensive central filtering unit which removes the entrained smaller particles and permits the thus cleaned air to escape into the atmosphere. The removed material is thereupon processed (e.g., classified according to size) prior to reintroduction into the cigarette making machine. Such procedure is costly and the material which is segregated from air in the central filtering unit is likely to change its characteristics (size and/or moisture content) prior to reintroduction into the machine.
It was already proposed to remove relatively small particles of tobacco from tobacco supply in the magazine of the distributor in a cigarette making machine and to admit the thus removed particles into the shower which is fed into the stream building zone, or to convey the particles back into the magazine. Such proposals have met with limited success because the removal of relatively small tobacco particles from the magazine takes place by gravity or by mechanical means neither of which insures removal of appreciable quantities of short tobacco and/or tobacco dust and also because a machine utilizing such recovering device for short tobacco and tobacco dust must also employ at least one relatively large, bulky and expensive central filtering unit since the aforediscussed suction air streams invariably segregate substantial quantities of short tobacco and tobacco dust which must be recovered before the suction air stream is recirculated or permitted to escape into the atmosphere.